• For Course materials: https://github.com/gl2668/R_For_Data_Science
• Me
  • Urban Planner & Data Analyst
  • Contact me via email: gl2668@columbia.edu
• You
  • Roundtable of names, interests, and background
  • Why do you want to learn R?

• Learning how to program / code in R!
• Learning some basic statistics and tools for data analysis
• Gain practical skills for career / research practice

• Download R
• Download R Studio
• Open R Studio and Explore the Console
• Helpful Reading: Hadley Wickham’s book

• R is a programming language that is commonly used for data science
• It is open-source, with a strong community of users and 14,837 packages available!
• It is free to use unlike Matlab, SPSS, Stata
• R is an easy first programming language to learn
• Less popular that Python but not second fiddle in my opinion (especially in the field of data science)
• Rstudio is an arguably better IDE than Jupyter (IMO it is the Apple to the Microsoft)

• R Studio is the IDE that allows you to code in R (and other languages like SQL and python)
  • IDE stands for Integrated Development Environment
  • Allows you to write functions and operations
  • Tidy and Visualize data

• You have the Console, Environment, Files and Packages

• R Markdown is the tool for you to report and present your code / output
  • File -> New File -> R Markdown -> Document -> HTML
• Set output to different file formats (with the Knit button)

• Need to learn markdown syntax
• Use the cheat sheet as a reference (google markdown cheat sheet)
• You can use Markdown to embed formatting instructions into your text. For example, you can make a word italicized by surrounding it in asterisks, bold by surrounding it in two asterisks, and monospaced (like code) by surrounding it in backticks:

*italics*, **bold**, `code`

• You can turn a word into a link by surrounding it in hard brackets and then placing the link behind it in parentheses, like this:

[Columbia U](www.columbia.edu)

To create titles and headers, use leading hastags. The number of hashtags determines the header’s level:

# First level header
## Second level header
### Third level header

To make a bulleted list in Markdown, place each item on a new line after an asterisk and a space, like this:

* item 1
* item 2
* item 3

You can make an ordered list by placing each item on a new line after a number followed by a period followed by a space.

1. item 1
2. item 2
3. item 3

You can also use the Markdown syntax to embed latex math equations into your reports. To embed an equation in its own centered equation block, surround the equation with two pairs of dollar signs like this,

$$1 + 1 = 2$$

To embed an equation inline, surround it with a single pair of dollar signs, like this: $1 + 1 = 2$

All standard Latex symbols work.

• R code can be included as chunk with

  ```{r} ```

  or inline with a single tickmark.

• R functions sometimes return messages, warnings, and even error messages. By default, R Markdown will include these messages in your report. You can use the message, warning and error options to prevent R Markdown from displaying these.

• Keyboard Shortcut to create a new chunk is command + option + I

Three of the most popular chunk options are echo, eval and results.

• If echo = FALSE, R Markdown will not display the code in the final document (but it will still run the code and display its results unless told otherwise).

• If eval = FALSE, R Markdown will not run the code or include its results, (but it will still display the code unless told otherwise).

• If results = 'hide', R Markdown will not display the results of the code (but it will still run the code and display the code itself unless told otherwise).

knitr is an engine for dynamic report generation with R and is used to convert (or “knit”) R Markdown files into the desired output format.

• html_document
• pdf_document
• word_document
• beamer_presentation / slidy_presentation / ioslides_presentation
• github_document

• Installing packages

#install.packages("dplyr")
library(dplyr)

• Or use a package manager, e.g. Pacman

#install.packages("pacman")
library(pacman)
p_load(dplyr, ggplot2)

• ggplot2 (graphics)
• tibble (data frames and tables)
• tidyr (make tidy)
• readr (read in tabular formats)
• purrr (functional programming)
• dplyr (manipulate data)
• tidyverse (All the above)

• R comes with several free datasets that are easy to practice and learn with
• For instance, mtcars
• To find out all the inbuilt dataset, just type data() in the console

head(mtcars)

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

• Reading data from the web

# Using the data.table package to read files
p_load(data.table)
flights <- fread("https://raw.githubusercontent.com/Rdatatable/data.table/master/vignettes/flights14.csv")

• Reading data from the Computer
• Check working directory / Set working directory

# Check working directory
getwd()

## [1] "/Users/geraldlee/Documents/Intro to R"

# Set working directory
setwd('/Users/geraldlee/Documents/Intro to R')

• Reading data from the Computer

# Using the readxl package to read in Excel files
library(readxl)
rawData <- read_excel(path = "data/data_example1.xlsx", # Path to file
                    sheet = 2, # We want the second sheet
                    skip = 1, # Skip the first row
                    na = "NA") # Missing characters are "NA"

# Or fread
rawData <- fread("data/data_example1.xlsx")

• Look at the help tab of your console

?ggplot2

help(dplyr)